Rudolf Marcel, Zumbusch Andreas
Department of Chemistry, Universität Konstanz, D-78457 Konstanz, Germany.
Langmuir. 2024 Aug 6;40(31):16085-16092. doi: 10.1021/acs.langmuir.4c00905. Epub 2024 Jul 25.
Colloidal dispersions composed of polymethylmetacrylate particles dispersed in a mixture of cyclohexyl bromide and decalin find widespread use as model systems in optical microscopy experiments. While the system allows simultaneous density and refractive index matching, preparing particles with hard potentials remains challenging, and strong variations in the physical parameters of samples prepared in the same manner are commonly observed. Here, we present data on the measurement of forces between individual pairs of particles in highly diluted dispersions over the course of tens of days using the blinking optical tweezers method. Our results show that the variations in the particle properties are indeed caused by a temporal evolution of the particles' charging. Additional measurements of the influence of the addition of tetrabutylammonium bromide (TBAB) to the dispersions show that already small concentrations of added TBAB salt drastically decrease the electrostatic forces between colloidal particles. However, small, non-negligible contact potentials remain even at the highest TBAB concentrations added.
由聚甲基丙烯酸甲酯颗粒分散在溴代环己烷和十氢化萘的混合物中组成的胶体分散体在光学显微镜实验中作为模型系统得到广泛应用。虽然该系统允许同时进行密度和折射率匹配，但制备具有硬势的颗粒仍然具有挑战性，并且通常会观察到以相同方式制备的样品的物理参数存在很大差异。在这里，我们展示了使用闪烁光镊方法在数十天的时间内对高度稀释分散体中单个颗粒对之间的力进行测量的数据。我们的结果表明，颗粒性质的变化确实是由颗粒电荷的时间演变引起的。对向分散体中添加四丁基溴化铵（TBAB）的影响的额外测量表明，即使添加的TBAB盐浓度很低，也会大幅降低胶体颗粒之间的静电力。然而，即使在添加的TBAB浓度最高时，仍然存在小的但不可忽略的接触电位。
